The present invention relates to a method of coating a cutter with a wear-protective layer of the type of the diamond film supported on a carrier or support made of metallic or non-metallic hard material and to a product produced by such method.
Cutting inserts for cutting tools, which are formed of metallic or non-metallic hard materials, have been known. Specific hard metals of sintered alloys, such as tungsten carbide, or cobalt, or tungsten carbide with titanium carbide and cobalt have been taken into consideration. Such cutting inserts are normally made of pure titanium carbide or, for example of aluminum oxide and titanium nitride or silicon nitride. However, in order not to handle pure metals the materials which have the highest elasticity module, such as boride, nitride or silicide, are to be considered.
It has been further known that cutting inserts made of materials of lesser hardness have been provided, to increase their resistance to wear, with a coating, for example of titanium nitride, or silicide nitride, or aluminum oxide or any other suitable material. Such coatings have been applied to carriers or supports of hard metals which have been normally utilized for machining steel, non-iron metals and other materials.
The application of such wear-protective layers to respective supporting elements has been obtained by known methods of chemical vapor deposition (CVD) or chemical plasma deposition or by reactive plasma sputtering.
In the chemical vapor deposition known as CVD, the production of thinner layers can be obtained by the chemical reaction of the gaseous components. This method finds application for example in the production of thin silicon layers in the semiconductor technology and also for the depositing of hydrocarbons of extreme hardness and high anisotropic heat conductivity.
It has been known from recent publications to use methane gas for depositing diamantine carbons whereby a desired material has been obtained under high vacuum and temperatures in the range of over 1,000 degrees C.
The so-called plasma-CVD method differs in that with a lower pressure, the heating of the gaseous phase is obtained by high frequency or electric charge such as the glow discharge, and ions of respective gaseous particles are deposited on respective supports so that metastable compounds, for example diamond can form.
In the third aforementioned known method, namely reactive plasma sputtering, the process of the cathode sputtering or disintegration is carried out, in which the rigid cathode is sputtered by ion bombarding and a layer is deposited on the substrate spaced from the cathode by few centimeters. This can take place in the gaseous phase of the reactive gas such as hydrogen or oxygen which is added to the plasma.
In practical applications of these recent technical developments the problem has arisen when for example cutting edges of the cutting or machining tools should be provided with wear-protective layers.
In addition to different heat expansion coefficients of the diamond and metals, further it should be taken into consideration that diamond has a very high elasticity module of about 10.5.times.10.sup.11 N/m.sup.2 whereas hard metals have the elasticity module about 4 to 5.times.10.sup.11 N/m.sup.2. Such substantial difference in elasticity modules leads to the fact that in such mechanical applications as treatments of metals or non-iron metals, forces which occur in such treatments lead to a premature breaking of the diamond films on their substrates which have a lesser elasticity modules or to the sputtering of the diamond film. Therefore, wear-protective layers of diamond applied to the suppports of the cutting tools, such as milling cutters, saws and the like, by any of known methods cannot be used in the industrial range.